In the aftermath of the shooting inside a Gurdwara in Wisconsin, more than 150 organisations have called for a Congressional hearing on hate crimes.

Six Sikh worshipers, including four Indian nationals, died when an ex-army man went on a shooting spree inside the Gurdwara in Oak Creek city in Wisconsin on August 5.

While the police is yet to determine the reason for the shooting, Sikh advocacy groups have termed it a hate crime.

Led by Washington-based Sikh Coalition, the 150 organisations representing a wide range of faith based and rights advocacy groups, yesterday sent a letter to the Senate Judiciary Committee to conduct hearings on hate crimes and the proliferation of hate groups in the US.

Citing the massacre of Sikh worshipers in Oak Creek, and a string of attacks on Muslim communities nationwide during the last month, the letter notes that hate violence continues to affect the lives of thousands of individuals due to their race, national origin, religious affiliation, sexual orientation, gender, gender identity, disability, and immigration status.

"We want to do everything in our power to make sure what happened in Oak Creek never happens to anyone again," said Rajdeep Singh, director of Law and Policy for the Sikh Coalition.

"Given the persistence of hate crimes and sheer number of hate groups in the United States, we want our policymakers to be proactive about uprooting bigotry in the United States.

"As First Lady Michele Obama visits the aggrieved families in Oak Creek this Thursday, we hope that Congress will do its part by looking at ways to improve our nation's hate crime laws," Singh said.

"During the last month alone, six worshipers at a Sikh Gurdwara in Wisconsin were massacred by an attacker with known ties to hate groups, and approximately ten Islamic institutions and Muslim communities in seven states have experienced attacks including vandalism, a suspicious burning, shootings, and the desecration of religious sanctuaries," the letter said.

The letter said according to the Southern Poverty Law Center, the number of hate groups in the US (currently numbering over a thousand) has grown by almost 60 per cent since 2000.

In 2010, more than 47 per cent of hate crimes were racially motivated; 20 per cent were motivated by the religion of the victim; 19 per cent were based on sexual orientation and almost 13 per cent of all hate crimes were based on ethnicity or national origin, it said.

"Given the persistence of hate crimes and the proliferation of hate groups, we believe that a hearing is both timely and necessary," the letter said.

We are especially interested in examining the status of the implementation of the Matthew Shepard Act; improvements to hate crime reporting and data collection; and the need for more robust hate crime prevention measures, consistent with protections for First Amendment rights and civil liberties, the organisations said in the letter addressed to the Senate Judiciary Committee.